Photographic enlarger



Jan. 30, 1951 w. D. THOMPSON 2,540,017

PHOTOGRAPHIC ENLARGER Original Filed Oct. 24, 1946 4 Sheets-Sheet l 4Z /4 S) mmum 4f ATTORNEY.

Jan. 30, 1951 w. D. THOMPSON 2,540,017

PHOTOGRAPHIC ENLARGER Original Filed Oct. 24, 1946 4 Sheets-Sheet 2 ml lllunm. Lil-lijn."- l

Jan. 30, 1951 w. D. THOMPSON 2,540,017

PHOTOGRAPHIC ENLARGER Original Filed Oct. 24, 1946 4 SheetS--Sheekl 3 /A/ vf/v 70H W/L UAM D. THOMPSON.

Jan. 30, 1951 w. D. THOMPSON 2,540,017

PHOTOGRAPHIC ENLARGER Original Filed Oct. 24, 1946 4 Sheets-Sheet 4 .Emil

Patented Jan. 30, 1951 PHOTOGRAPHIC ENLARGER William D. Thompson, San Diego, Calif.

Substituted for application Serial No. 705,441, Oc-

tober 24, 1946. This application January 13,

1948, Serial N0. 1,947

3 Claims.

This invention relates to a photographic enlarger, and this application is a substitute for applicants original application led October 24, 1946, under Serial No. 705,441, now abandoned. The principal object of the present invention resides in the provision of an enlarging apparatus which will be exceedingly rigid in construction and which can be easily and accurately adjusted to obtain maximum lighting efliciency and accurate focus at all positions so that perfect, clearcut enlargements may be quickly and easily produced.

Other objects of the invention are:

To provide adjusting means which will allow` exceedingly accurate positioning of the easel, the lamp house, and the lamp so that highly eii'icient results in focusing, framing, sizing, and light spread may be accomplished;

To provide an efficient and compact assembly having storage space for paper and supplies, a safe working light for use in positioning the paper on the table, a timing switch, an accurate focus indicator, and a roll film holde1` all combined in a single, unitary, easily-operated machine;

Io provide in an enlarger of this type a film holder which will be completely dust-tight; whicn Will eliminate the possibility of finger prints on the film; which will provide means for cleansing the film each time it is used; and which will provide a convenient method of storing each roll of negatives; and

To provide a pressure plate which can be brought to bear against the portion of the film being enlarged so as to hold it on a true, flat plane provided with means for releasing the pressure plate when it is desired to move the film to prevent scratching thereof.

Other objects and advantages reside in the detail construction of the invention, which is designed for simplicity, economy, and eiiciency. These will become more apparent from the following description. A

In the following detailed description of the invention, reference is had to the accompanying drawing which forms a part hereof. Like numerals refer to like parts in all views of the drawing and throughout the description.

In the drawings:

Fig. 1 is a fragmentary side view of the improved enlarger;

Fig. 2 is a front view thereof; Fig. 3 is a fragmentary top view of the enlarger;

Fig. 4 is an enlarged detail sectionalview of a supporting arm employed on the enlarger, taken on the line 4 4, Fig. 1;

Fig. 5 is a similarly enlarged detail section taken on the line 5 5, Fig. 1;

Fig. 6 is an enlarged longitudinal, vertical section taken on the line 6 6, Fig. 3;

Fig. 7 is a fragmentary detail section taken on the line 1 1, Fig. 6;

Fig. 8 is a similar section taken on the line 8 8, Fig. 6;

Fig. 9 is a detail view partly in section illustrating the mounting of a lamp house supporting arm employed in the improved enlarger; and

Fig. 10 is a side view of a focusing device which may be used with the improved enlarger.

The improved enlarger is supported from a relatively heavy base member I0 having an upstanding, sleeve-like socket II formed thereon. A Vertical, tubular standard I2 is positioned in and extends rigidly and vertically from the socket I I, it being securely locked therein by means of suitable set screws I3. The standard I2 may, if desired, be provided at its top with a wall bracket I4, by means of which it may be rigidly secured to a convenient wall or other support.

A split, table-supporting guide sleeve I4 is slidably mounted on the standard I2. The split in the guide collar I5 may be contracted by means of a clamp bolt I6 havingV an integral wrench handle I1. Two table-supporting brackets I8 are formed on and extend outwardly in a V-shape from the collar I5 to support a table board I9. A drawer case 20, having a plurality of forwardlyopening drawers 2|, is mounted below the table board I9.

A stop sleeve 22 may be clamped about the standard I2 at any desired vertical position thereon. The sleeve 22 is positioned above the collar I5 and acts as a pre-set stop therefor.

A spring arm 23 is formed on and projects upwardly and rearwardly from the sleeve 22, and a similar spring arm 24 projects downwardly from the collar I5. A tension spring 25 is stretched between the extremities of the two arms 23 and 24 and serves to counteract the weight of the table I9 and its drawer case 20.

A resilient cushion ring 26 separates the sleeve 22 and the collar I5, and a similar resilient cushion ring 21 is positioned above the socket Il. The sleeve 22 can be pre-set at a desired enlargement point. The collar I5 can then beadjusted about the standard I2 to any desired position without losing the focus since the spring 25 will maintain the collar I5 at the proper elevation. When set, the collar may be locked by the clamp li bolt I6. Should the sleeve and collar be accidentally dropped the impact will be absorbed.

The lamp house clamp 28 carries a springactuated click ball device 50 which engages a vertical groove in the standard |2 when the lamp house is in the proper center position over the table i9.

A split lamp house clamp 28 is slidably and rotatably mounted on the standard I2 and may be clamped in any desired position thereon by means of a second clamp bolt 29 which is ro; tatable from a bolt handle 3|). A bracket arm 3| projects from the clamp 28 and supports a horizontal, tubular guide member 32. Ihe guide member 32 slidably supports a horizental, lamp house supporting arm 33.

The arm 33 terminates in'a 4forked-head member 34 provided with a vertical, threaded passage for receiving a threaded adjusting screw 3,5, and with two spaced-apart, vertical guide passages `for receiving twoguide bars 36. It is preferred to form the arm 33 a's an integral cast pu of the head member 34 and to surround the bar with a wear resisting sleeve of steel or the like as indicated at 95 in Fig. 4. The bar s 3B are secured in upper and lower lampI house brackets 31 positioned above and below the head member 34. The screw 35 is rotatably mounted in the brackets 31 and terminates in a -hand vwheel 38 at its lower extremity.

It can be readily seen that, as the screw is. rotated in one direction, it will cause the brackets 31 to move upwardly, guided by the bars 39;y and when rotated in the other directionjwill cause these brackets to move downwardly.

The brackets 31 are attached to and suppert a lamp housing 39. The weight of the -larnplhousf ing 43 9 and its supporting structure is eounter balanced by means of a counterweighrt secured on the extremity of a counter-weight cable 4|. The counter-weight 49 is suspended within the hollow standard l2 and its cable 4| rides over a guide pulley 42 at the top thereof., terminating in a cable bracket 43 on the guide member 32.

The supporting arm 33 is rotatable in theniember 32. Its position in the member .is indicated by means of a pointer line 44 engraved longitudinauy in the member 33. The pointer iineinf dicates positions on an annular index scale 4 5 onV the member 32. This enables the lamp housing 39 to be rotated to any desired angle` from the vertical for producing special effectsZ forcor-v recting distortions in the imagesand for pref jecting an image onto a side wall o r screen,

The vertical position of the lamp housing is automatically indicated by means of a click ball 46, which is urged by means of a spring 41 intel a longitudinal groove i8 in the top ef thesup-r porting arm 33. The arm is also adjustable 1on-r gitudinally in the member 32 for properly positioning the image on the table I9. It may -be locked in any desired extended or angular posi tion by means of a hand wheel screw 49.l

The lamp house contains an automotive type lamp 52 supplied with reduced voltage current from a suitable transformer 53 which is mounted on the back of the lamp house within the Vconnes of the head member 34 and the brackets 31.

The lamp is carried in a suitable receiving socket 54 mounted on a cross-head 55. The cross-head is moved vertically in the lamp house by means of a threaded shaft 56 rotatable from a hand wheel 51 on the exterior of the lamp house` The vertical movement o f the cross-head is guided by means of two slide rods i8 supportedby rod brackets 94 affixed to the back of the lamp house 39.

A square post 59 extends upwardly from the cross-head 55 to support a vertically adjustable reflector bracket 69. The bracket 99 supports a parabolic reilector 9|, through the medium of reflector clamps 62 and a sliding clamp frame 93 which is mounted on a supporting rod 64 extending from the bracket 99. The bracket can be raised and lowered on the square post 59 and set in any desired position thereon by means of a setl screw 65 and the frame `63 can be adjusted along and rotated about the rod 89 so as to position the reflector 6| at the proper focal point with reference to the lamp 52.

" A condenser lens barrel 89 is removably attached to the bottom of the lamp house by means of nsuitable thumb screws 61. The barrel 96 con.

tains conventional condensing lenses 98. A lens head chamber 69 is removably attached to the bottom of the barrel 95 by means of a second set of suitable thumb Screws 19.

The vlewer portion of the chamber E9 is transversally slotted, as shown at 1|, to receive a nlm holder "12 containingthe film to 'be enlarged indicated at |99. The bottom of the chamber 59 is closed by meansV of a head plate 13 secured thereto by'means of suitable thumb screws 93. The head plate 13 carries an internally threaded lens *collarv 14 in which an objective lens barrel 15 is threaded.` The barrel 15 carries a conventional objective lens system 16. Rotation of the lens barrel 15v raises or lowers the objective lens system 16 to properly focus an image of the nlm '|09 on the table I9.

The current to the lamp 52 is automatically controlled by means of a timing device l1 mounted in a timer housing 'i9 on the front of the lamphouse l39. The controls of the timer 11,' indicated at 19, are mounted on a control panel -8'9 in the iront of the timer housing 19.

The mechanism of the timing device 11 is more fully rillustrated and described in applicants copendin application, Serial No. 713,642, now abandoned.

The control panel is illuminated by means of a pilot lamp 9|, positioned in .a lig-ht shield 99 positioned below the housing 1t, .through an upwardly facing window 92. The light 4from the lampdi'also shines through a downwardly facing vruby glass window k83 to illuminate .the table |9 "with a safe photographic light. The pilot lamp is controlled from a pilot lamp switch 94.

.The lamp house is provided with heat radiation fins 85u. The chamber .59 'is provided with a removable door Q9 held in place by means of snap springs 81 and provided `with va suitable handle 91. For focusing the enlarger, the door 85 is removed and a reiiecting focusing device, such as llstrated. Fgf 19 iS, lsld iufm the Chamber G9 @is/'shown in. broken line in Fis. 6-

IThe'focusing device is ldescribed. more in detail in applicants 'co-pending application, Serial No. 705,442, now Patent No. 2,499559,A issued January 3, 1950. Briefly, iit consists of a plate 83 vwhich snapsfinto place fin place of the door 86. The plate carries a lens tube |39 and an eye piece 99. The lens vtub'e supports a 45 yreiiecting mirror 9|. The focusing devicemakes use of the fact that the objective lens system 19 will project an image of the illuminated picture-on the table board |9 onto the lm in the holder 12. The ymirror 9| will reflect this imag@ ask well as an image of ihelm Aemulsion through theeye ,piece su to the operator. The lens system is then adjusted to bring these two images into perfect alignment to insure perfect focus.

The lm holder 'l2 comprises a housing having a lm spool at each end operated by Winding knobs 52 by means of which the lm may be caused to travel across the path of the light from one spool to the other. This iilm holder is described more in detail in applicants co-pending application, Serial No. 705,443, now Patent No. 2,461,668, issued February 15, 1949. It is believed that the convenience, accuracy and versatility of the improved enlarger will become apparent from the above description, as minutely accurate controls are provided for every adjustment. The usual enlarger has no provision for altering the position of the light source' for varying film areas. An approximation only is obtained. A full utilization of the light and a perfect uniform light spread can only be obtained by having the light source at the exact focal point of the condensing lens system when the light from the latter is concentrated on the film area. Since the area varies with different sizes of films an accurate adjustment of light focus must be provided. This is true with this improved enlarger.

Three adjustments are provided to obtain convenient table height and accurate focus, that is, the collar l5, the clamp 28 and the hand wheel 38. An automatic return to a pre-set minimum after the table has been temporarily lowered to obtain a special enlargement of a portion of a speciiic print. The spring 25 and the counterweight 49 both contribute to a reduction of the manual effort required by the operator.

Indentations 96 are milled into the bottom of the click ball groove in the standard I2 at pre-determined points for automatically registering the lamp housing clamp 28 at pre-determined enlarging positions, such as ve inches by seven inches, eight inches by ten inches, eleven inches by fourten inches, etc., so that the operator can quickly position the lamp housing for any desired enlargement, the iinal adjustment, of course, being made by means of the hand wheel 39. The click ball device 50 does not prevent the bracket arm 3| from being swung from side to side, as angular pressure on the arm will release the click ball from the groove 5l, as is usual with conventional click ball devices.

In the conventional enlarger the lm is locked in close proximity to the condensing lenses. In this improved enlarger the film is locked a considerable distance below the condensing lenses, due to the height of the lens head chamber 69. This places the negative at the concentrated position of the light beam from the condensing lenses at a position where the beam will just cover the entire negative. This greatly increases the brilliance of the negative, since all of the available light is concentrated upon the negative at this point. This avoidance of the usual light waste of the conventional enlarger allows a much smaller source of light to be used in the improved enlarger with equal results.

The base member I0 is provided with a plurality of electric outlets 99 which provide convenient means for attaching cords to other devices.

While a specific form of the improvement has been described and illustrated herein, it is desired to be understood that the same may be varied,

with the scope of the appended claims, without departing from the spirit of the invention.

Having thus described the invention, what is claimed and desired secured by Letters Patent is:

1. In a photographic enlarging machine of the type described, a lamp house; a table board; a vertical, tubular standard; a lamp house clamp surrounding said standard; a bracket member extending from said lamp house clamp; a horizontally positioned tubular guide member carried by said bracket member; a cylindrical supporting arm rotatably and horizontally adjustable Within said guide member; means for supporting said lamp house from said supporting arm; and a. spring-actuated click ball device carried by said lamp house clamp and engaging said standard, there being a vertical guide slot in said standard for receiving said ball so as to guide said bracket member in a vertical plane, and there being spaced-apart depressions in said slot for receiving said ball device for supporting said lamp house at pre-set positions.

2. Means I'or supporting a lamp house in an enlarging machine comprising: a vertical tubular standard; a lamp house clamp surrounding said standard; a bracket member extending from said lamp house clamp; a horizontally positioned tubular guide member carried by said bracket member; a cylindrical supporting arm rotatably and horizontally adjustable Within said guide member; means for supporting said lamp house from said supporting arm; means for clamping said supporting arm in said guide member; and a click ball device carried by said guide member and engaging said supporting arm, there being a longitudinally extending groove in said supporting arm for receiving said click ball device when said lamp house is in the vertical position.

3. Means for supporting a lamp house in an enlarging machine comprising: a vertical, tubular standard; a lamp house clamp surrounding said standard; a bracket member extending from said lamp house clamp; a horizontally positioned tubular guide member carried by said bracket member; a cylindrical supporting arm rotatably and horizontally adjustable within said guide member; a Y-shaped head member carried by said supporting arm and lying normally in a horizontal plane; a guide bar extending vertically through each fork of the Y-shaped head member; lamp house brackets securing the upper and lower extremities of said guide bars to said lamp house; and screw means threaded through said head member for moving said guide bars vertically through said head member.

WILLIAM D. THOMPSON.

REFERENCES CTTED The following references are of record in the iile of this patent:

UNITED STATES PATENTS Gelb Dec. 4. 1945 

